LOS ANGELES — Alejandro Cisneros calls the newer arrivals “pirates.” They simply put on a costume and trick customers into thinking they are mariachi musicians, he says, but they know nothing of the history of Mexican music.

Juan Ariso calls the old-timers “the businessmen.” They are too focused on charging more money and pushing out those who they believe are taking gigs they do not deserve, playing at weddings and quinceañeras and the occasional backyard cookout.

The two groups cannot agree on many things, but the most important is this: How much should a mariachi charge?

“This is our profession, our job, our passion,” Mr. Cisneros said. “We don’t want to have it ruined by these people who do not know what they are doing.”

For Mr. Ariso, it is a simple business calculation: “I charge what they are willing to pay. That changes all the time.”

For generations, musicians have gathered each day in a corner of the Boyle Heights neighborhood, just east of downtown. The sprawling square has been called Mariachi Plaza for as long as anyone can remember and has served as a central band-gathering spot since the 1940s.